Magnetic disk drives used as external recording apparatuses for information-processing equipment such as computers, have been requested to increase recording capacity. To meet this request, increases in recording density have been contemplated. If the conventional longitudinal magnetic recording system is used to promote increased density, a demagnetizing field in the magnetic transition region on a medium is large. Therefore, it is necessary to reduce the thickness of a recording layer, which consequently produces a problem in that recorded data is lost due to thermal fluctuation. On the other hand, a perpendicular magnetic recording system in which a recording-magnetizing direction is a medium's thickness direction makes it easy to achieve high-recording density. This is because since a demagnetizing field in the magnetic transition region is small, a necessity to reduce the thickness of a medium is relatively small.
When a perpendicular recording magnetic head is used to record a signal in a perpendicular recording medium, the electric signal is converted into a magnetic signal by a coil to excite a magnetic flux at main and auxiliary magnetic pole pieces. Part of the magnetic flux flows from the auxiliary magnetic pole piece to the main magnetic pole piece, passing through a perpendicular recording layer of the recording medium. The part of the magnetic flux passes through a soft magnetic underlayer below the perpendicular recording layer and returns to the auxiliary magnetic pole piece, thus providing a closed loop. In this case, the auxiliary magnetic pole piece is used to magnetically-efficiently return the magnetic flux generated, from the main magnetic pole piece, in the perpendicular recording layer and soft magnetic underlayer of the recording medium, to the main magnetic pole piece again. Such flow of the magnetic flux records a signal as magnetization on the perpendicular recording medium.
To increase the recording density in the perpendicular recording system, it is necessary to process a write head as well as a read head to provide its element height with a high degree of precision. Japanese Patent Publication No. 2006-48806 (“Patent document 1”) describes the following: A read head-specific detection pattern for air-bearing surface processing and a write head-specific detection pattern for air-bearing surface processing are provided at a portion to become a slider. The detection pattern for air-bearing surface processing on the write head side is used to lap the air-bearing surface while monitoring the element height (throat height) of the write head. In this case, both the element height (throat height) of the write head and the element height (sensor height) of the read head can be controlled by monitoring the read head-specific detection pattern for air-bearing surface processing. In addition, the resistances of processing detection patterns for the write and read heads are detected during the lapping of the air-bearing surface of the heads. If it is found that the throat height of the write head is larger than the sensor height of the read head, the write head is lapped to reduce the throat height with the lapping surface tilted.
Japanese Patent Publication No. 2005-339781 (“Patent document 2”) describes the following: A first electric lapping guide (ELG) is located near the sensor of a read head and a second ELG and a first optical lapping guide (OLG) are provided near the main magnetic pole piece of a write head. The resistance value of the first ELG is correlated with the resistance value of the second ELG and the width of the first OLG. On the basis of the correlation, the throat height of the write head is controlled independently while controlling the sensor height of the read head. In addition, a lapping surface is tilted to compensate for an element height-wise positional deviation occurring when a main pole region is formed above the sensor.
In the conventional technologies described above, the lapping surface of a row bar or slider is tilted and pressed against a lapping surface table for lapping in order to control the element heights of the read head and write head. In this case, a corner of the row bar or slider is likely to come into contact with and damage the lapping surface table at certain inclination angles. When the row bar or slider is tilted to the leading end side for lapping, since the ELG formed on the trailing end side is not lapped, the resistance value of the ELG remains unchanged. Thus, while the leading end side is lapped, the ELG signal is not obtained. Therefore, the control of the element height will be unstable.